Employee Benefit Plans (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Employee Benefit Plans [Line Items]
Deferred Compensation Arrangements, Overall, Description	For participants who reside in the United States, the Company may credit participants with discretionary contributions provided the participant is employed on the last day of the plan year and has deferred the maximum permissible amount to the Company's qualified 401(k) plan for such year. Discretionary contributions are derived from a pool that is equal to an aggregate of 4.5% of the compensation of each participant for the plan year that exceeds the limitation on compensation under Code Section 401(a)(17) for such year. For participants outside of the United States, the Company's matching contributions will be an amount determined by the Company. Company matching contributions to the Deferred Compensation Plan are 100% vested.
Description of Defined Contribution Pension and Other Postretirement Plans	Duff & Phelps, LLC, a subsidiary of the Company, sponsors the Duff & Phelps Savings Plan, a qualified defined contribution 401(k) plan covering substantially all employees (“401(k) Plan”). Employees are entitled to make contributions up to 100% of their compensation subject to Internal Revenue Code (“Code”) limitations. The Company matches an amount equal to an employee's contribution up to 3% of the employee's compensation and matches 50% of the employee's contribution up to the next 3% of compensation. All Company contributions are discretionary. Participants are immediately vested in both their voluntary and matching contributions plus actual earnings thereon.
Defined Contribution Plan, Employer Discretionary Contribution Amount	$ 4,814	$ 4,644	$ 4,610

- Definition

Description of the terms and benefits provided by the employer's defined contribution plans. A defined contribution plan provides benefits in return for services rendered, provides an individual account for each participant, and has terms that specify how contributions to the individual's account are to be determined rather than the amount of benefits the individual is to receive. Under a defined contribution pension plan, the benefits a participant will receive depend solely on the amount contributed to the participant's account, the returns earned on investments of those contributions, and forfeitures of other participants' benefits that may be allocated to such participant's account. A description of the plan(s) including employee groups covered, the basis for determining contributions, and the nature and effects of significant matters affecting comparability of information for all periods presented.

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